In certain welding operations, it is often necessary or desirable to remove or replace oxygen from a welding location to prevent oxidation of the weld as welding occurs. Oxidation of the weld can affect the integrity of the weld, and makes it more difficult to ensure that a given weld is defect free. Historically, this problem has been solved by using welding machines that incorporate large chambers surrounding the weld application site. In operation, any air and gas in those chambers is purged with an inert gas (such as argon), such that the chamber is filled with only the inert gas. Then, the welding can occur in a pure inert gas atmosphere, preventing any oxidation of the weld. Of course, a substantial drawback of this solution is that it requires significant amounts of expensive inert gases—together with a significant amount of equipment, preparation, evacuation time and/or effort. Likewise, where welding operations encircle a workpiece, requiring the purging of oxygen in the immediate welding region, the use of specialized inert gas conduit equipment, with gas-tight bearing sections may be required.
For instance, European Pat. No. EP 0787058 describes a device for use in joining pipes in a butt-welded joint. The described device may be utilized for shutting off one of two pipes or cylindrical sections to be joined by welding, and by supplying purge gas. The purge gas is distributed through evenly distributed radial nozzles into a gap of limited radial depth, so that the purge gas flows laminarly or quasi-laminarly past the welding line. The composition of the purge gas is sensed at the free end of the gas sampler or sensor located well downstream of the welding site. Additionally, set-up times for use of the device can be considerable.
U.S. Pat. No. 3,521,020, meanwhile describes another device for butt welding tubes. The described gas purge assembly is inserted into the interior of a work piece, which prevents oxidation of the interior of the weld. The assembly, however, distributes inert gas around the full 360 degree interior of the pipe to be welded, including vast regions well-distanced from the immediate weld site—to waste appreciable amounts of the inert gas being used. Likewise, set-up and turnaround times for use of the assembly can be substantial.
Still further, International Publication No. WO 90/06205 describes a method and tool for welding pipes. As described, in order to ensure the necessary gas coverage when welding stainless steel such as pipes, a method and apparatus are employed which comprises a rear gas apparatus provided with copper jaws which are provided with outlet openings for gas and coolant pipes which cool the welding zone and the gas. The welding apparatus can be provided with gas coverage in the form of a casing which is supplied with gas, and which is also provided with a coolant pipe for the cooling of the welding zone and the gas. Set-up and turnaround times with this method and tool can be excessive.
U.S. Pat. No. 5,711,474 similarly describes a method and apparatus for welding tubular members. In particular, the apparatus includes an array of gripping members 62, which are adapted to grippingly contact the inner surface of pipes to be welded together. Each of the gripping members 62 includes gas passageways, which are formed to exit through an outlet which is positioned to cause the existing gas to travel in a somewhat annular helical path within a valley. The pipes to be welded together are placed over the exterior of the tool and a localized purge gas source distributes inert gas around the full 360 degree interior of the pipe to be welded, displacing oxygen immediate not only the weld, but also elsewhere. Further, considerable set-up and turnaround times can be required.
Still further, US Patent Publication No. 2003/0127493 describes a gas purge welding ring, for placement within pipes to be welded. The described gas purge tool, however, is merely a ring having an adjustable circumference. Specifically, side walls of the ring extend to the inner surface of the pipe being welded, thereby creating an isolation zone, which is filled with inert gas. Still, the welding ring may require significant set-up and turnaround times.
Finally, Chinese Patent Publication No. 201940754 describes a gas purge tool disposed within a pipe to be welded, including a semi-automatic welding argon filling device. The welding device for two butt-welded alloy tubes includes an argon gas filling device flexibly arranged in the alloy tube, wherein the argon gas filling device is composed of a motor and rotatable telescoping swing arm on a motor housing. Three telescoping stabilizers extend from the motor housing. The telescopic swing arm is arranged on the mechanical output end of the motor, an argon filling box is fixed on the outer end of the telescopic swing arm, and an argon spray outlet is arranged on the top of the argon filling box opposite to the inner arm of the alloy tube to be welded. An argon input port is arranged on the argon filling box and the top of the argon filling box with the argon spray outlet arranged above the inner side of the weld back. The motor is utilized to rotate the argon filling box around the inner surface of a pipe to be welded. Accordingly, the pipe remains stationary, while the argon filling box and the welding tool rotate simultaneously, in alignment, around the pipe work piece, which is restrained in a fixed position. The alignment and use of such a tool can require substantial set-up and turnaround times.
In view of at least the foregoing references, there is a demonstrable need for an improved localized gas-purge welding device as presently disclosed herein.